EFFECT OF THERMO-MECHANICAL TREATMENT ON PROPERTIES OF PARICA PLYWOODS (Schizolobium amazonicum Huber ex Ducke)

Abstract

-Thermo-mechanical treatment is a technique for wood modification in which samples are densified by means of heat and mechanical compression, applied perpendicularly to fibers, which under different combinations of time, temperature, and pressure increases wood density and thus improve some of its properties. This study aimed to treat thermo-mechanically parica plywood and observe the effects on its physical and mechanical properties. Specimens were submitted to two treatments, 120 and 150 °C, remaining under pressure for seven minutes and, subsequently, under zero pressure for 15 minutes. Results showed a significant increase in specific mass from 0.48 g cm -3 to an average of 0.56 g cm -3 , and a compression ratio of about 31.7% on average. Physical properties also varied significantly and results showed that treated samples swelled and absorbed more water than those untreated, leading to a greater thickness non-return rate. This indicates the proposed thermal treatments did not release the internal compressive stress generated during panel pressing, not improving its dimensional stability as a result. On the other hand, mechanical properties were positively affected, leading to an increase of 27.5% and 51.8% in modulus of rupture after treatments at 120 and 150 °C, respectively. Modulus of elasticity and glue-line shear strength did not vary statistically and Janka hardness was 29.7% higher after treatment at 150 °C.Keywords: Thermo modification; Wood panels; Densification EFEITO DO TRATAMENTO TERMO-MECÂNICO SOBRE AS PROPRIEDADES DE COMPENSADOS DE PARICÁ (Schizolobium amazonicum Huber ex Ducke)RESUMO -O tratamento termomecânico é uma metodologia para modificação da madeira, onde as amostras são densificadas por meio do calor e da compressão mecânica aplicada perpendicularmente às fibras, que submetidas a diversas combinações de tempo, temperatura e pressão aumentam a densidade da madeira e assim melhoram algumas de suas propriedades. O presente trabalho teve como objetivo tratar termomecanicamente compensados de paricá e observar os efeitos nas suas propriedades físicas e mecânicas. Os corpos-de-prova foram submetidos a dois tratamentos: a 120°C e a 150°C, mantidos sob pressão por sete minutos e, posteriormente, sob pressão zero, por quinze minutos. Os resultados mostraram que houve aumento significativo da massa específica de 0,48g/cm 3 para, em média, 0,56 g/cm 3 , e a taxa de compressão foi de 31,7% em média. As propriedades físicas também variaram significativamente, e os resultados mostraram que as amostras tratadas incharam e absorveram mais água que as testemunhas, levando a uma maior TNRE (taxa de não-retorno em espessura). Isto indica que os tratamentos térmicos propostos não liberaram as tensões internas de compressão geradas durante a prensagem do painel, não melhorando sua estabilidade dimensional. As propriedades mecânicas, por sua vez, foram afetadas positivamente, levando a um aumento de 27,5% e 51,8% do MOR após os tratamentos a 120°C e a 150°C, respectivamente. O MOE e o cisalhamento...

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